Engineering of Au/Ag Nanostructures for Enhanced Electrochemical Performance

The effect of nanostructuring on the electrochemical activity of a series of Au/Ag electrocatalysts, with and without graphene nanoplatelets (G) as carbon matrix support and β-cyclodextrin as capping agent, was systematically investigated using the ferri/ferrocyanide redox probe. A series of Au/Ag nanostructures with different morphologies were synthesized and characterized using a combination of spectroscopy, electron microscopy, and electroanalytical methods. Evaluation of the cyclic voltammograms obtained from the ferri/ferrocyanide redox probe using electrodes modified with the different Au/Ag nanostructures revealed significant enhancement in peak currents upon using hollow Au/Ag nanobox and porous-hollow Au/Ag nanocage analogs in comparison to conventional solid spherical Au nanoparticles. The observed improvements in electrochemical activities can be attributed to the nanoreactor cage and edge effects in the hollow cubic nanostructures. Moreover, the dispersion of the nanostructures in G and their surface modification with β-cyclodextrin further enhanced their electrochemical performance. The best performing Au/Ag nanostructure that was modified with β-cyclodextrin and G was used to fabricate an electrochemical sensor for the stress biomarker cortisol. The resulting electrochemical sensor exhibited good linear response to cortisol in the concentration range of 1 pM to 100 nM, making it a promising platform technology for monitoring the physiological stress indicator.